Athermalized integrated optical waveguide devices

ABSTRACT

The present invention provides an athermalized organic-containing overclad integrated planar optical waveguide circuit device in which thermal induced shifting of channel wavelengths is minimized. The organic-containing overclad material is combined with a silica or doped silica glass material in the form of a local overclad, a bi-layer overclad, or a hybrid overclad. The organic-containing overclad material is a polymer or a sol-gel material.

FIELD OF THE INVENTION

[0001] The present invention is directed to integrated optical waveguidedevices in which the light transmitting properties are insensitive totemperature variations and fluctuations. More particularly, the presentinvention is directed to athermalized integrated planar opticalwaveguide devices with organic-containing overclads containing silicateglasses, polymers, and/or hybrid (organic/inorganic) sol-gels.

BACKGROUND OF THE INVENTION

[0002] Integrated optical waveguide devices, such as integrated opticalcircuits, combine miniaturized waveguides and optical devices into afunctional optical system incorporated onto a small planar substrate.Such integrated optical waveguide devices are utilized in, for example,optical communications systems, usually by attaching optical waveguidefibers that transmit light signals to the integrated optical waveguidedevice as inputs and outputs. The integrated optical waveguide deviceperforms a function or process on the transmitted light in the opticalcommunications system.

[0003] Integrated optical devices which incorporate optical path lengthdifferences can be used as, for example, wavelength multiplexing anddemultiplexing devices. Such integrated optical devices are particularlyuseful as wavelength division multiplexers (WDM)/demultiplexers, and mayincorporate a phased array made from a plurality of different waveguidecore arms which have differences in optical path length.

[0004] Wavelength division demultiplexers include, in particular, atleast one input waveguide, which transmits N optical signals at Ndifferent wavelengths (λ₁, λ₂, . . . λ_(N)), and at least N outputwaveguides, each transmitting one of the N optical signals at apredetermined wavelength λ₁ (i=1, 2, . . . N). Conversely, wavelengthdivision multiplexers include at least N input waveguides, eachtransmitting one of the N optical signals at the wavelengths λ₁, λ₂, . .. λ_(N), and at least one output waveguide, which transmits the Noptical signals. The wavelengths λ₁, λ₂, . . . λ_(N) of the N opticalsignals preferably are equal to the channel center wavelengths, wherethe transmission spectra of the real device show the lowest losses. Anyperturbation inducing a change in the channel center wavelengths of thedevice is preferably avoided.

[0005] WDMs, such as phasars, require precise control of the opticalpath difference (OPD) between adjacent waveguide paths of the phasedarray. The OPD can be expressed as n×ΔL, where n is the effective indexof the fundamental mode in the optical waveguide path, and ΔL is thephysical path length difference between adjacent waveguide paths. Themean channel wavelength λ₀ is determined by mλ₀=OPD=n×ΔL, where m is thediffraction order. Any shift of the mean channel wavelength induces thesame shift on the channel center wavelengths. Since n and ΔL usuallyboth depend on temperature, the available integrated optical waveguidedevices require temperature regulation to avoid a wavelength shift withtemperature. Although such devices provide good performance atconsistent standard room temperatures, the devices exhibit poorperformance when used in environments where they are exposed to thermalvariations and fluctuations in temperature. In such integrated devices,thermal shifts of the channel center wavelengths of greater than onetenth of the channel spacing at a transmitting wavelength in the 1550 nmrange can limit their usefulness in environments of differingtemperature. Silica-based phasars show a channel wavelength shift ofabout 0.01 nm/° C., while channel spacings are currently of 0.4 to 1.6nm, which limits their use to small temperature ranges. Thus, use ofintegrated optical waveguide devices is limited by their temperaturedependence.

[0006] Presently, the application of integrated optical waveguidedevices has been hindered by the requirement to consistently maintainthe temperature of the device such as by actively heating or cooling thedevice. While such costly and energy consuming heating and cooling maysuffice in a laboratory setting, there is a need for an integratedoptical waveguide device that is manufacturable and can be deployed inthe field and operate properly when subjected to temperature changes.Accordingly, the present invention is directed to athermalizedintegrated optical devices that can be manufactured, packaged, and/orused without the requirement for temperature control.

SUMMARY OF THE INVENTION

[0007] The present invention is directed, in part, to an integratedoptical waveguide device that substantially obviates one or more of theproblems due to the limitations and disadvantages of the related art.The present invention provides, in part, an athermalized integratedoptical waveguide device comprising a thermal shift compensatingnegative dn/dT organic-containing overclad, such as a polymer orsol-gel, which inhibits the shifting of channel wavelengths due tovariations in operating temperature within a predetermined operatingtemperature range. In a preferred embodiment of the invention, anathermalized phased array wavelength division multiplexer/demultiplexeris provided.

[0008] Additional features and advantages of the invention will be setforth in the description that follows, and in part will be apparent fromthe description or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the apparatus, compositions, and methods particularlypointed out in the written description and claims hereof as well as theappended drawings.

[0009] To achieve these and other advantages and in accordance with thepurposes of the invention, as embodied and broadly described, theinvention provides an integrated optical waveguide circuit device thatincludes a doped silica waveguide circuit core supported on a planarsubstrate. The planar substrate is preferably a solid flat substrate(such as a silica wafer or a silicon wafer) which may further include anunderclad or buffer layer (such as an undoped or lightly doped silicalayer). The doped silica waveguide circuit core has a first waveguidepath and at least a second waveguide path, wherein the waveguide pathshave a difference of ΔL of path length that is selected to provide anoptical path difference which corresponds to suitable channelwavelengths λ in the range of 1500-1600 nm and to a suitable freespectral range (with respect to the number of channels and to thechannel spacing).

[0010] Preferred optical waveguide devices of the invention include athermal shift compensating negative dn/dT organic-containing overclad,such as a polymer or sol-gel, which may be used in combination with adoped silica (or silicate glass) partial overclad. Theorganic-containing overclad (together, if applicable, with the dopedsilica partial overclad) clads the doped silica waveguide circuit core.The organic-containing overclad is preferably made of a polymermaterial, or of a sol-gel material, and is preferably used incombination with a silicate glass as a local overclad, a bi-layeroverclad, or a hybrid overclad. The overclad covers and encapsulates thewaveguide circuit core. Preferably, the organic-containing overclad hasa negative variation in refractive index versus temperature (dn/dT). Theorganic-containing material and the geometrical parameters of the deviceare selected such that the organic-containing material's negativevariation in refractive index versus temperature (dn/dT) restricts theshift in the channel center wavelengths to less than 0.10 nm, preferablyless than 0.05 nm, when the device is subjected to a temperaturevariation within the operating range of 0° C. to 70° C.

[0011] In a preferred embodiment of the invention, the device is awavelength division multiplexer/demultiplexer with the waveguide pathsforming a phased array. In other preferred embodiments of the invention,the athermalized integrated optical phased array wavelength divisionmultiplexer/demultiplexer comprises a doped silica waveguide core on aplanar substrate that is overcladded, in part, with a silicate glassoverclad, and in part with a polymer comprised of fluorinated monomersor with a hybrid organic/inorganic sol-gel.

[0012] Other preferred athermalized optical telecommunicationswavelength division multiplexer/demultiplexer integrated waveguidecircuit devices comprise a doped silica waveguide circuit core supportedon a planar substrate, wherein the silica waveguide circuit coreincludes a multiplexing/demultiplexing circuit region (phased array) formultiplexing/demultiplexing a plurality of optical telecommunicationswavelength channels. The device also comprises an inhomogeneouswaveguide circuit overcladding including a first waveguide overcladdingmaterial and a second waveguide overcladding material. The device guidesoptical telecommunications light in a waveguide core power distributionand in a waveguide overcladding power distribution, wherein a firstportion of light guided in the waveguide overcladding power distributionis guided through the first waveguide overcladding material and a secondportion of light guided in the waveguide overcladding power distributionis guided through the second waveguide overcladding material such that athermally induced wavelength shift in the channel wavelengths of themultiplexing/demultiplexing device is inhibited to less than 0.10 nmwhen the device is subjected to a temperature variation within the rangeof 0 to 70° C. The thermally induced wavelength shift in the channelwavelengths of said multiplexing/demultiplexing device can be inhibitedto less than 0.05 nm. The first waveguide overcladding material ispreferably an organic containing optical material and the secondwaveguide overcladding material is preferably an inorganic opticalmaterial. The first waveguide overcladding material preferably has anegative variation in refractive index versus temperature and the secondwaveguide overcladding material preferably has a positive variation inrefractive index versus temperature. The first waveguide overcladdingmaterial negative variation in refractive index versus temperature ispreferably less than −5×10⁻⁵° C.⁻¹ and the second waveguide overcladdingmaterial positive variation in refractive index versus temperature isusually more than 5×10⁻⁶° C.⁻¹.

[0013] The present invention also comprises a method of making anoptical waveguide wavelength division multiplexer/demultiplexer device.The method includes the steps of providing a planar substrate, andforming a doped silica waveguide core on the planar substrate with thewaveguide core incorporating an optical path length difference whichcorresponds to suitable channel wavelengths λ in the range of 1500-1600nm. The method further includes overcladding the doped silica waveguidecore with a polymer overclad having a negative variation in refractiveindex versus temperature (dn/dT), wherein the polymer overclad inhibitsthe shift of the channel center wavelengths when the device is subjectedto a variation in temperature.

[0014] In a preferred embodiment of the invention, a method of making anathermalized optical telecommunications wavelength divisionmultiplexer/demultiplexer integrated waveguide circuit device comprisesproviding a waveguide circuit core supported on a planar substrateincluding a waveguide undercladding, which can be a buffer layer or thesubstrate itself. The waveguide circuit core material and the waveguideundercladding material preferably have a positive variation inrefractive index versus temperature. The waveguide circuit corepreferably includes a multiplexing/demultiplexing circuit region formultiplexing/demultiplexing a plurality of optical telecommunicationswavelength channels. An inhomogeneous waveguide circuit overcladdingincluding a first waveguide overcladding material and a second waveguideovercladding material is provided. The first waveguide overcladdingmaterial preferably has a negative variation in refractive index versustemperature and the second waveguide overcladding material preferablyhas a positive variation in refractive index versus temperature. Thepositive variation in refractive index versus temperature of thewaveguide circuit core, of the waveguide undercladding material and ofthe second waveguide overcladding material are compensated by thenegative variation in refractive index versus temperature of the firstwaveguide overcladding material, wherein either 1) light is guided bythe waveguide circuit core, the waveguide undercladding material and thefirst waveguide overcladding material in one part of the device, andguided by the waveguide circuit core, the waveguide undercladdingmaterial and the second waveguide overcladding material in the otherpart of the device; or 2) the first waveguide overcladding material issuperimposed on the second waveguide overcladding material such that afirst portion of light is guided by the waveguide circuit core, thewaveguide undercladding material and the second waveguide overcladdingmaterial, while a second portion of light is guided by the firstwaveguide overcladding material; or 3) the second waveguide overcladdingmaterial is mixed to the first waveguide overcladding material toproduce a hybrid waveguide overcladding material and light is guided bythe waveguide circuit core, the waveguide undercladding material and thehybrid waveguide overcladding material, such that a thermally inducedwavelength shift in the channel wavelengths of themultiplexing/demultiplexing device is inhibited to less than 0.10 nmwhen the device is subjected to a temperature variation within the rangeof 0 to 70° C. The thermally induced wavelength shift in the channelwavelengths of the multiplexing/demultiplexing device is preferablyinhibited to less than 0.05 nm.

[0015] The accompanying drawings are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention, andtogether with the description serve to explain the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 depicts preferred monomer units of preferred polymercladdings of the invention which include pentafluorostyrene (5FS),trifluoroethylmethacrylate (3FEMA), glycidyl methacrylate (GMA),pentadecafluorooctylacrylate (15FOA), pentafluorobenzylacrylate (5FBA),trifluoroethylacrylate (3FEA), and hexafluoropropylacrylate (6FPA).

[0017]FIG. 2 shows a plot of the mean channel wavelength versustemperature for a phased array wavelength division demultiplexer devicewith a doped silica overclad (dotted line; dλ/dT=+0.01 nm/° C.), for aphased array wavelength division demultiplexer device overcladded withthe fluorinated copolymer epoxy 9 of the invention (solid line withcrosses), and for a phased array wavelength division demultiplexerdevice overcladded with the fluorinated copolymer epoxy 10 of theinvention (solid line with diamonds).

[0018]FIG. 3A is a schematic top view of a preferred integrated opticalwaveguide circuit phased array wavelength divisionmultiplexer/demultiplexer device. Also shown is the position of the maskused for local overclad deposition.

[0019]FIG. 3B shows a cross-sectional left side view of the device ofFIG. 3A along dashed line AA′ which comprises an uphold enabling themask to be held above the ridge.

[0020]FIG. 4 shows a cross-section schematic view of a preferredwaveguide with a preferred bi-layer organic-containing overclad.

[0021]FIG. 5A shows a cross-section view of a preferred waveguide with athick glass overclad, showing the small pattern remaining at theoverclad surface above the waveguide.

[0022]FIG. 5B shows a cross-section of the preferred waveguide depictedin FIG. 5A after etching.

[0023]FIG. 5C shows a cross-section of the preferred waveguide depictedin FIG. 5B after depositing a layer of an organic-containing material,thus achieving a bi-layer overclad.

[0024]FIGS. 6A and 6B show graphs of desired theoretical n(T) (indexversus temperature) curves of the organic-containing material forathermalization in the etched glass overclad bi-layer method, with 3 μm(6A) and 5 μm (6B) thick glass overclad and different n(0° C.) valuesfor the organic-containing material.

[0025]FIG. 7 shows a plot of the mean channel wavelength versustemperature for a phased array wavelength division demultiplexer devicewith a bi-layer overclad of the invention comprising an etched silicateglass part and a polymer part consisting of fluorinated copolymer epoxy16.

[0026]FIG. 8 is a cross-section view of a preferred waveguideovercladded by the thin glass overclad method of the invention.

[0027]FIG. 9 shows a graph of desired theoretical n(T) (index versustemperature) curves of the organic-containing material forathermalization in the thin glass overclad bi-layer method, with a glassoverclad of 0.5 μm thickness and different n(0° C.) values for theorganic-containing material.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0028] The present invention comprises, in part, athermalized integratedoptical waveguide devices comprising an organic-containing overcladwhich inhibits the shifting of channel wavelengths due to variations inoperating temperature within a predetermined operating temperaturerange.

[0029] Integrated optical waveguide devices are well known to theskilled artisan and are described in detail throughout the literature.Exemplary integrated optical waveguide devices preferably include adoped silica waveguide circuit core on a planar substrate, preferably aflat planar silica substrate, such as a fused silica member, or asilicon wafer with a silica buffer layer.

[0030] In preferred embodiments of the invention, the integrated opticalwaveguide device is a phased array wavelength divisionmultiplexer/demultiplexer with a circuit core having a phased array ofwaveguide paths. Such devices are well known to the skilled artisan. Insome preferred embodiments of the invention, the silica waveguidecircuit core is comprised of a first waveguide path and at least asecond waveguide path which are preferably adjacent and substantiallyparallel. The present invention, however, encompasses a phased array ofa multitude of waveguide paths, with the phased arrays having upwards ofseveral hundreds of waveguide paths. In the case of a demultiplexerdevice, a wavelength multiplexed signal is inputted into the device viaan input waveguide with the multiplexed signal comprised of multiplewavelengths λ₁, λ₂, . . . λ_(N). A coupler region then couples themultiple wavelength signal into the waveguide paths of the phased array.The phased array demultiplexes (separates) the wavelengths λ₁ throughλ_(N) such that they are coupled through a second coupler into theirindividual channel output waveguides that exit the device. Conversely,in the case of a phased array multiplexer, the wavelengths λ₁ throughλ_(N) are inputted into the device via their individual channel inputwaveguide and coupled into the waveguide paths of the phased array by afirst coupler region. The phased array combines the wavelengths λ₁through λ_(N) such that they are coupled through a second coupler into acommon output waveguide. In both the demultiplexer and the multiplexerdevices, the phased array waveguide paths have a path length differenceΔL that is selected to provide an optical path difference whichcorresponds to the wavelengths λ₁, λ₂, . . . λ_(N) of the multiplexedsignal. The optical path difference is preferably selected to correspondto suitable wavelengths λ₁, λ₂, . . . λ_(N) in the range of 1500-1600 nmand to a suitable free spectral range.

[0031] The variation of mean channel wavelength with temperature incommercially available optical devices is expressed in the followingEquation 1, where λ is the mean channel wavelength and T thetemperature:

dλ/dT=λ(1/n×dn/dT+1/ΔL×dΔL/dT)  (1)

[0032] Both the effective index n and the physical path lengthdifference ΔL are temperature dependent. The value of dn/dT is about10⁻⁵° C.⁻¹ for silica and can range approximately between −4×10⁻⁴° C.⁻¹and −5×10⁻⁵° C.⁻¹ for polymers. The second term, “1/ΔL×dΔL/dT,” whichcorresponds to the coefficient of thermal expansion of the substrate, isabout 5.5×10⁻⁷° C.⁻¹ for a silica substrate. It can be neglected infirst approximation or can be canceled with a slightly negative dn/dT.The organic-containing overclads of the invention provide a negativevariation of their refractive index versus temperature. The opticalwaveguide devices of the invention comprise a planar substrate(comprising at least a silica substrate or a silica underclad), a dopedsilica core, and an overclad comprising at least an organic-containingpart, and if applicable a silicate glass part. The fundamental modeeffective index of the optical waveguide devices of the inventiondepends on the doped silica core material index (positive dn/dT), on thesilica underclad or substrate material index (positive dn/dT), ifapplicable on the silicate glass overclad material index (positivedn/dT) and on the organic-containing overclad material index (negativedn/dT). The optical signals in the preferred devices propagate not onlyin the core, but also in the clad. The organic-containing overcladcompensates for the thermal effects (index and physical path) on thesilica-containing parts (underclad, core, and if applicable overclad),and cancels the temperature dependence of the device, so that the shiftof channel center wavelengths is inhibited to less than about 0.1 nm,preferably less than about 0.05 nm at temperatures in the working rangeof 0° to 70° C. Since silica presents a positive dn/dT, the use oforganic-containing overclad materials, such as polymers or sol-gels,which have negative dn/dT values, makes it possible to cancel thethermal deviation of channel wavelengths in a mixed silica-polymersystem. Thus, the inventive organic-containing overclad compositionsallow precise adjustment of the overclad index, and provide for theathermalized characteristics.

[0033] In preferred embodiments of the invention, the optical waveguidedevices comprise an organic-containing overclad which clads the silicawaveguide circuit core. The organic-containing overclad preferablyencapsulates the silica waveguide circuit core supported by a planarsubstrate wherein light guided by the silica waveguide circuit core, theorganic-containing overclad, and the planar substrate propagates in thesilica waveguide circuit core, organic-containing overclad, and planarsubstrate.

[0034] In preferred embodiments of the invention, the organic-containingoverclad has a negative variation of refractive index versus temperature(dn/dT), and is selected such that the organic-containing overclad dn/dTinhibits the shift of channel center wavelengths to less than about 0.10nm, preferably less than about 0.05 nm when the device is subjected totemperature variations in the range of 0° to 70° C. More preferably, theorganic-containing overclad and the negative variation of refractiveindex versus temperature dn/dT are selected to inhibit shifts of channelcenter wavelengths to less than about 0.01 nm.

[0035] The precise range of organic-containing overclad index useful forathermalizing devices depends on parameters such as core index, coredn/dT and core dimensions. In particular, the upper limit is determinedby losses in curved waveguides and depends on the radius of curvature ofwaveguide circuit core. In a preferred embodiment, the core index isabout 1.35 to 1.60, preferably about 1.40 to 1.50. More preferably thecore index is about 1.455±0.002 at 1550 nm, 20° C., with core dn/dTassumed to be equal to that of silica (10⁻⁵° C.⁻¹), and core dimensionsare about 6×6.5 μm. In this case, the refractive index of theorganic-containing overclad is in the range of 1.430 to 1.450 at 1550nm, 20° C., most preferably between about 1.437 and about 1.447 at 1550nm, 20° C.

[0036] Preferred organic-containing overcladdings of the inventioncomprise polymers and/or copolymers containing fluorinated monomers,preferably wherein the fluorinated monomers are selected from thevinylic, acrylic, methacrylic or allylic families (group consisting ofvinylics, acrylics, methacrylics and allylics). The copolymerscontaining fluorinated monomers are preferably synthesized with afree-radical process (thermally-induced or photo-induced). Theorganic-containing overclads can be comprised of polymers or copolymerscontaining other families such as fluorodioxole. If the refractive indexof the core material is higher than 1.5 at 1550 nm (with a differentdoping of the core material), new families could be used such asfluorinated polyimides. Pentafluorostyrene (5FS),trifluoroethylmethacrylate (3FEMA), pentadecafluorooctylacrylate(15FOA), pentafluorobenzylacrylate (5FBA), (see FIG. 1), combinationsthereof, and the like are the preferred fluorinated monomers of theorganic-containing overclads of the invention. One skilled in the art,however, is able to use other fluorinated monomers, such astrifluoroethylacrylate (3FEA) or hexafluoropropylacrylate (6FPA) (seeFIG. 1), in organic-containing overclads of the invention.

[0037] The choice of the monomers comprised in the copolymer affects notonly the refractive index but also the dn/dT of the copolymer. Typicallypolymers present dn/dT in the range of −1×10⁻⁴° C.⁻¹ below theirtemperature of glass transition (Tg) and in the range of −3×10⁻⁴° C.⁻¹above their Tg. By changing the polymer formulation, it is possible toadjust the Tg, then the dn/dT. Pentafluorostyrene, methacrylates, shortside chains (methyl or ethyl) on the monomers tend to increase the Tg ofthe copolymer. 5FS, 3FEMA are preferred monomers for high Tg—lessnegative dn/dT copolymers. Acrylates, long side chains monomers tend tolower the Tg of the copolymer. 5FBA, 15FOA, 6FPA, are preferred monomersfor low Tg—very negative dn/dT copolymers.

[0038] Preferred organic-containing overclads are improved when adifunctional methacrylate-epoxy monomer is added, particularly when thedifunctional methacrylate-epoxy monomer is glycidyl methacrylate (GMA)(see FIG. 1). Although not intending to be bound by theory, it isbelieved that the difunctional methacrylate-epoxy monomer provides forcationical and/or thermal cross-linking of the copolymers after theorganic-containing overclad has been deposited over a doped waveguidecore and planar substrate. One skilled in the art, however, is able touse other difunctional monomers providing for the cross-linking of thecopolymers of the invention. The overclad is preferably laid from thecopolymers in solution. Typically, the overclad is cast by spin coating,alternatively by dip-coating. The solvent used to dissolve and lay thecopolymer of the invention may be selected from tetrahydrofuran,chloroform, methylene chloride, toluene and other aromatic solvents,solvents from the ester and the ketone families. Good results areobtained with ethyl acetate, butyl acetate, or butanone.

[0039] An improved polymer overclad is also obtained when using anadhesion promoter. The preferred adhesion promoters are from the silanefamily. Good results are obtained with glycidoxypropyl trimethoxy silane(GlyMo), mercaptopropyl trimethoxy silane (MPMo), gamma-aminopropyltrimethoxy silane (GAPS) and the like. The adhesion promoters can beused as a surface treatment on the device before casting the polymeroverclad. Alternatively, the adhesion promoter can be mixed to thesolution of the polymer of the invention used to coat the device andform the overclad.

[0040] A preferred organic-containing cladding of the inventioncomprises about 25-65 wt. % of trifluoroethylmethacrylate (3FEMA), about10-75 wt. % of pentafluorostyrene (5FS) and about 0-30 wt. % of glycidylmethacrylate (GMA). The monomer mixture is preferably polymerized viafree-radical process. A preferred free-radical initiator is about 0.1-5wt. % 4,4′-azobis (4-cyanovaleric acid) (ADVN) overall monomerconcentration. The polymerization is preferably run in solution. In apreferred embodiment, the polymerization mixture is comprised of 50-95wt. % tetrahydrofuran (THF).

[0041] Another preferred organic-containing cladding of the inventioncomprises about 30-80 wt. % of pentafluorostyrene (5FS), about 20-40 wt.% of pentadecafluorooctylacrylate (15FOA) and about 0-30 wt. % ofglycidyl methacrylate (GMA). The monomer mixture is preferablypolymerized via free-radical process. A preferred free-radical initiatoris about 0.1-5 wt. % 4,4′-azobis(4-cyanovaleric acid) (ADVN) overallmonomer concentration. The polymerization is preferably run in solution.In a preferred embodiment, the polymerization mixture is comprised of50-95 wt. % tetrahydrofuran (THF).

[0042] In preferred embodiments of the invention, the organic-containingovercladding comprises a copolymer referred to herein as “Copolymerepoxy 9”. Copolymer epoxy 9 is prepared by polymerizing about 60 wt. %5FS, about 30 wt. % 3FEMA, and about 10 wt. % GMA. 1 wt. % of ADVN freeradical initiator is added to the mixture which is dissolved in THF. Theoverall concentration of monomer in THF is usually in the range 5-50 wt.%. The solution is stirred and warmed at 70° C. for 16 hours. Thecopolymer is then isolated and purified by precipitation in methanol.The copolymer refractive index n at 1550 nm, 20° C. is 1.447, asmeasured with a m-line prism coupler, and the dn/dT is about −1×10⁻⁴°C.⁻¹, as measured by the backreflectance technique.

[0043] In other preferred embodiments of the invention, theorganic-containing overcladding comprises a copolymer referred to hereinas “Copolymer epoxy 16”. Copolymer epoxy 16 is prepared by polymerizingabout 67 wt. % 5FS, about 29 wt. % 15FOA, and about 4 wt. % GMA. 1 wt. %of ADVN free radical initiator is added to the mixture which isdissolved in THF. The overall concentration of monomer in THF is usuallyin the range 5-50 wt. %. The solution is stirred and warmed at 70° C.for 16 hours. The copolymer is then isolated and purified byprecipitation in methanol. The copolymer refractive index n at 1550 nm,20° C. is ca. 1.44, and the dn/dT at 1550 nm is −1.4×10⁻⁴° C.⁻¹, asmeasured using the backreflectance technique.

[0044] Another preferred organic-containing cladding of the inventioncomprises about 45-100 wt. % of pentafluorobenzylacrylate (5FBA), about0-25 wt. % of pentadecafluorooctylacrylate (15FOA) and about 0-30 wt. %of glycidyl methacrylate (GMA). Typically, the dn/dT of a copolymerprepared by polymerizing 60 wt. % 5FBA, 35 wt. % 15FOA, and 5 wt. % GMA,is about −3×10⁻⁴° C.⁻¹.

[0045] In another preferred embodiment of the invention, a sol-geloverclad, preferably a hybrid sol-gel material, is employed as theorganic-containing overclad rather than a polymer. A unique capabilityof the hybrid sol-gel materials is that the dn/dT can be continuouslytuned by varying the composition from pure SiO₂ to R—SiO_(2/3), where Ris an organic side group. The most significant change in thiscomposition range is the average network coordination number, which forsilica is 4 and for the silsesquioxane is 3. The addition of one networkcoordinate bond increases the compaction and stiffness of the matrix,and is the primary factor that differentiates physical properties. Onephysical property that affects the index of refraction is thecoefficient of thermal expansion, through the molar volumetricrefractivity. It has been recognized that the dn/dT scales with the CTE.Therefore, compositional approaches can be developed to tune the dn/dTby using average network coordination to affect the CTE of the material.Pure SiO₂ has an expansion of 5.5×10⁻⁷/° C., whereasR—SiO_(2/3)compounds have expansions in the 200×10⁻⁶/° C. range.Incorporation of four-fold coordinate silica into three-fold coordinatehybrid shifts the expansion to significantly lower values and thereforeshifts the dn/dT towards +1×10⁻⁵/° C. (the value for silica) from−3×10⁻⁴/° C. (the value for silsesquioxanes). A nearly linearrelationship of CTE with the average network coordination number in acomposition has been measured. Similarly, the value of dn/dT can beassumed to depend on the SiO₂ content of the hybrid material. A desiredvalue of dn/dT can be made by appropriately balancing the three andfour-fold coordinate silicon atom content in the composition. Theorganic sidegroups R can be chosen to set the index of refraction, andto slightly modify the dn/dT. To make a hybrid sol-gel material withdn/dT of −1×10⁻⁴/° C., a composition with 60% SiO₂ and 40% R—SiO_(2/3)is needed. To further refine the composition so that an index of 1.444is achieved, the 40% three-fold coordinate silicon may be comprised of75% ethylsilsesquioxane, and 25% phenyl silsesquioxane. Precursors withother organic sidechains may be used, and their effect on the index mayrequire independent optimization. A typical formulation for theabove-mentioned hybrid material with dn/dT=−1×10⁻⁴/° C., and n=1.444 isprovided below. Briefly, 40.4 cc of TEOS is diluted with 60 cc IPA andis reacted with between 1.5 and 2.0 cc H₂O and 0.28 cc HNO₃. Thereaction is allowed to proceed for 60 minutes at 45° C. before additionof between 1.5 and 2.0 cc H₂O. After an additional 30 minutes ofreaction at 45° C., 0.9 cc of PDMS, 17.4 cc of ETMS, and 6.4 cc of PTESare added. Finally, between 3.8 and 4.5 cc of H₂O are added and reactedfor 30 minutes before cooling. Prior to use, the sol is distilled to 50%of its volume to afford a water clear sol. The choice of water contentprimarily affects the cure rate properties of the material, faster ratesbeing achieved with higher water content.

[0046] The mechanism used for tuning the dn/dT is to compositionallychange the average network connectivity of the silicon atoms. The silicacomponent of the hybrid is supplied by the tetraethoxysilane precursorand the silsesquioxane component by alkoxyorganosilanes. Since bothreact via hydrolysis and condensation reactions, the mixture of thethree- and four-fold coordinate silicon atoms in the final product isexpected to be microscopically homogeneous. Therefore, properties suchas the index of refraction are expected to be uniform over sub-microndistances in the optical path, which is critical for retention ofacceptable performance in optical circuits.

[0047] The sol-gel based compositions of the invention possess lowoptical loss, a means of controlling the index of refraction, and anegative shift of the index of refraction with increased temperature.The compositions of the invention include, but are not limited to, thosecompositions recited in WO 98/26315, WO 98/25862, and U.S. ProvisionalApplication No. 60/118,946 filed Feb. 5, 1999 of S. Dawes and R.Hagerty, each of which is incorporated herein by reference in itsentirety. These compositions are particularly suitable in the presentinvention because of the low optical loss at 1550 nm, good thermaldurability, good resistance to damp heat environments, ability to tailorindex of refraction compositionally, and negative thermal coefficient ofindex of refraction (dn/dT).

[0048] The dn/dT value of a composition comprising molar fractions ofabout 8% polydimethylsiloxane, about 68% methyltriethoxysilane, about 8%phenyltrifluorosilane, and about 16% phenyltriethoxysilane was measuredin a ball termed backreflectance apparatus. A cleaved end of a fiber wasdipped into a sol precursor, and cured to 250° C. The sol-gel ball termserved to scatter all transmitted light. A standard backreflectancemeasurement then provided information on the reflected light from thefiber/sol-gel interface. The ball termed fiber was placed into an ovenalong with an independent thermocouple, and reflectance measurementsacquired at several temperatures between 20° C. and 100° C. The value ofthe index can be calculated from the reflectance using the equation:R=(n₂−n₁)/(n₂+n₁). A substantially linear temperature dependence of theindex was found, and the value of the dn/dT was established as −3×10⁻⁴/°C. This value is both opposite in sign and much higher in magnitude thanthe dn/dT of silica. The magnitude of the negative dn/dT is explained bythe high thermal expansion coefficient (200×10⁻⁶/° C.) of the curedhybrid sol-gel materials. The rapid change in volume reduces the molarrefractivity of the material and induces a negative change in the index.

[0049] To demonstrate that organic-containing materials can be used toeffect a change in the dλ/dT properties of a phasar, a preferred devicewas prepared as follows. A silica wafer was provided with a core layer,which was etched to a desired waveguide pattern using standardlithography and reactive ion etch techniques widely known to thoseskilled in the art. A hybrid sol-gel overclad layer was cast onto thecore structure to provide a 20 to 50 μm thick layer. The index ofrefraction of the sol-gel layer was 1.447 at 1550 nm and 21° C. The cladlayer in such a structure carries about 10% of the light in a singlemode. The device was trimmed on the input and output to reveal thewaveguides and then the sample was measured. The phasar performance wasmeasured at 21° C., 40° C., and 50° C. The phasar provided well-definedsignals on the output channels, with rather high loss and adjacentchannel crosstalk, and good nonadjacent channel crosstalk. In addition,the wavelength shift in each channel was −3.5×10⁻²/° C., which isopposite the shift in silicate based core/clad compositions, and roughlythree to four times greater in magnitude. Both the size and thedirection of the wavelength shift are in rough agreement with theanalysis of the dn/dT and f+/f− characteristics of the waveguide.

[0050] The loss in the device was 6 dB higher than would be expected ina silicate overclad device, and the losses can arise from coatingthickness non-uniformity, machining damage to the substrate/overcladinterface, inexact index match, and intrinsic loss of the sol-gelmaterial. The adjacent crosstalk was affected by bubble flaws that wereentrapped in the overclad layer in the phase array section of thedevice. The good non-adjacent crosstalk values indicate that the indexhomogeneity was minimal. Despite the high expansion of the sol-gel, verylow polarization effects were observed. The results indicate that thestresses on the system were roughly a third less than that in silicatesystems. This result agreed with the independent stress measurementsmade on films of hybrid sol-gel materials on silica. Low stresses arisefrom the low temperature process along with low modulus of the hybridmaterial.

[0051] Another phased array demultiplexer was overcladded with a polymerhaving a dn/dT of the order of −1×10⁻⁴° C.⁻¹. The phasar was prepared bypatterning a doped silica core layer by photolithography and reactiveion etching. The core layer was supported on a fused silica substrate.The core layer index (at 1550 nm) and thickness were 1.453 and 6.8 μmrespectively, as measured with a m-line prism coupler. The waveguidelinewidth was found to be 6.1 μm. The phased array device was thenovercladded with the copolymer epoxy 9 of the invention described above,by spin-coating a solution of 35 wt. % of copolymer epoxy 9 in 65 wt. %of ethyl acetate on the device.

[0052] The device overcladded with copolymer epoxy 9 was measured at 23,53 and 71° C. The temperature was varied by laying the device on aPeltier element. A plot of the mean channel wavelength versustemperature is shown in FIG. 2 (solid line with crosses). The slope ofthe curve is −0.02 nm/° C., which is still opposite in sign to the shiftin a silicate glass overcladded device (FIG. 2, dotted line).

[0053] In order to further reduce the wavelength temperature dependenceof the devices, another phasar was overcladded with a polymer having adn/dT of the same order as copolymer epoxy 9 (ca. −1×10⁻⁴° C.⁻¹), and asmaller refractive index at 1550 nm, 20° C. A smaller clad index inducesa smaller fraction of guided light in the clad, and thus a smallerweight of the polymer negative dn/dT in the effective dn/dT of thewaveguide. As previously the phasar was prepared by patterning a dopedsilica core layer supported on a silica substrate. The core layer index(at 1550 nm) and thickness were 1.453 and 6.8 μm respectively. Thewaveguide linewidth was found to be 6.3 μm. The polymer that was used tooverclad this phasar device is referred to herein as “Copolymer epoxy10”. Copolymer epoxy 10 was prepared by polymerizing about 35 wt. % 5FS,55 wt. % 3FEMA, and 10 wt. % GMA. The same procedure as for copolymerepoxy 9 was used to prepare the copolymer and spin-coat the device. Thecopolymer layer refractive index at 1550 nm, 20° C. was 1.434.

[0054] The device overcladded with copolymer epoxy 10 was measured at15, 25, 50 and 70° C. A plot of the mean channel wavelength versustemperature is shown in FIG. 2 (solid line with diamonds). Thesemeasurements show that the mean channel wavelength remains in a range of0.05 nm between 15 and 70° C. Copolymer epoxy 10 thus enablesathermalization of phased array multiplexer/demultiplexer devices.

[0055] However, the fundamental mode of waveguides overcladded withcopolymer epoxy 10 is assumed to be very asymmetrical due to the lowrefractive index of this copolymer, especially at temperatures aboveroom temperature. As a result, the coupling loss with a standard (SMF28) fiber is increased by ca. 0.3 dB per interface, as estimated usingan optical modeling software. Thus, using a copolymer with a refractiveindex close to silica (at least near room temperature), such ascopolymer epoxy 9, is desirable.

[0056] In order to compensate for the negative wavelength-temperaturedependence occuring with organic-containing overclad materials ofrefractive index close to silica, and of dn/dT values smaller than ca.−8×10⁻⁵° C.⁻¹, such as copolymer epoxy 9 or the hybrid sol-gel materialdescribed above, the organic-containing overclad material may beassociated to a silicate glass material with positive dn/dT, asdescribed hereafter.

[0057] Different patterns of organic-containing overclad are within thepresent invention and include local overclad, bi-layer overclad, andhybrid overclad. Local overclad is characterized by local deposition ofa silica clad on a portion of the device followed by a coating withorganic-containing overclad on the remainder of the device. Bi-layeroverclad is characterized by a bilayer made of a first layer of silicaand a second layer of organic-containing overclad material. Hybridoverclad is characterized by a clad made of silica nano-particlesembedded in a polymer matrix. The term organic-containing material moreparticularly describes polymers and hybrid organic/inorganic sol-gels.

[0058] Local Overclad

[0059] In the local overclad method, a glass overclad is deposited onlylocally on the waveguides as shown in FIG. 3A, in order to provide theorganic-containing material in a limited region of the overclad. Morelight can be exposed to the organic-containing region, over a shorterlength. This can be accomplished by masking the region during depositionof the glass overclad. The mask, which can be a thin silica sheet, canbe held above the waveguides by means of upholds, as shown in FIG. 3B.If the sheet is thin enough, it can be cut far from the waveguides andremoved after glass overclad deposition. The portion of the device thatwas masked during glass overclad deposition is then overcladded with theorganic-containing material.

[0060] The position of the edges of the silica sheet that cross thewaveguides must be precisely determined in order to obtain a constantpath length difference in the glass overcladded region ΔL_(g), and aconstant path length difference in the organic-containing overcladdedregion ΔL_(p) with ΔL_(g)+ΔL_(p)=ΔL. The mean channel wavelength λ₀ isnow determined by m×λ₀=n_(g)×ΔL_(g)+n_(p)×ΔL_(p), where n_(g) is theeffective index of glass overcladded waveguides and n_(p) is theeffective index of organic-containing overcladded waveguides. In orderto obtain an athermalized device, the ratio of ΔL_(p) to ΔL_(g)preferably equals in first approximation (neglecting the CTE term) theratio of dn_(g)/dT to −dn_(p)/dT. An advantage of the local overcladmethod is that near the edges of the device, the overclad can compriseglass. Thus, standard pigtailing techniques (used for full glassdevices) can be employed to connect the input and output waveguides withthe fibers that carry the optical signal.

[0061] Bi-Layer Overclad

[0062] In another embodiment of the invention, the organic-containingoverclad is applied using the bi-layer method. In this method, a glassoverclad layer and an organic-containing overclad layer are superimposedas shown schematically in FIG. 4. The configuration is tailored so thatonly the desired fraction of light passes through the negative dn/dTregion to balance the effective index of refraction according toEquation II: f−×(dn−/dT)=f+×(dn+/dT), where the fraction in the negativedn−/dT material is indicated by f− and the fraction in the positivedn+/dT materials is indicated by f+. Preferably, a bi-layer overclad canbe applied in two different manners: etched glass overclad and thinglass overclad.

[0063] In the etched glass overclad method, a thick glass overclad isfirst deposited on the waveguides. Typically, a small pattern remains atthe overclad surface along the waveguides (see FIG. 5A). Then the glassoverclad is etched until reaching the top side of the waveguide core(see FIG. 5B). An optional lithography masking method can be used toetch the device in the phased array region only, for easier pigtailingat the device input/outputs. Since only etching is needed to removeoverclad, no highly precise patterning is needed. The device is thenovercladded with an overclad material of the invention.

[0064] The effective index of such waveguides with the approximate shapeof FIG. 4 has been calculated using optical modeling software. Thefollowing sets of parameters were used:

[0065] wavelength: 1550 nm

[0066] core width and height: 6 μm×6.5 μm

[0067] silica CTE: 5.5×10⁻⁷° C.⁻¹

[0068] silica substrate and glass overclad indices at 0° C.: 1.444

[0069] core index at 0° C.: 1.455 (corresponding to a Δ of 0.75%)

[0070] silica substrate, glass overclad and core dn/dT's: 10.5×10⁻⁶°C.⁻¹ (assumed to be equal to silica dn/dT in the visible range)

[0071] organic-containing overclad index at 0° C.: 1.443, 1.444, or1.445

[0072] glass overclad thickness remaining on both sides of thewaveguides after etching: 3 μm or 5 μm.

[0073] For each of the six sets of parameters (corresponding todifferent organic-containing material indices and glass overcladthicknesses), the effective index at 0° C. was first calculated. Then athigher temperatures T (from 10 to 70° C. by steps of 10° C.) theeffective index n_(eff)(T) desired for athermalization was calculatedusing Equation 1 and the organic-containing material index desired toobtain the effective index n_(eff)(T) was calculated with commerciallyavailable optical modeling software. The results are shown in FIG. 6A (3μm thick glass overclad) and 6B (5 μm thick glass overclad). FIGS. 6Aand 6B show that the dn/dT of the organic-containing material preferablybecomes more negative at higher temperatures, which is the case forutilized polymers. The average dn/dT between 0 and 70° C. is preferablyabout (−1.8±0.2)×10⁻⁴° C.⁻¹ in the case of 3 μm thick glass overclad andpreferably about (−3.3±0.2)×10⁻⁴° C.⁻¹ in the case of 5 μm thick glassoverclad. An advantage of the present method is that pigtailing isfacilitated because the edges of the device are overcladded with glass.

[0074] A phased array demultiplexer was overcladded using the etchedglass overclad method. The phasar was prepared by patterning a dopedsilica core layer by photolithography and reactive ion etching. The corelayer was supported on a fused silica substrate. A glass overclad wasthen deposited by flame hydrolysis deposition, consolidated at 1240° C.for ¾ hr and then partially etched away, leaving about 2 μm of overcladabove the waveguides. The phased array device was then overcladded withthe copolymer epoxy 16 (described above) by spin-coating a solution of35 wt. % of copolymer epoxy 16 in 65 wt. % of ethyl acetate on thedevice.

[0075] The device overcladded with copolymer epoxy 16 was measured at15, 23, 50, 70 and 80° C. A plot of the mean channel wavelength versustemperature is shown in FIG. 7. The slope of the curve is +0.007 nm/°C., which is slightly smaller than the shift in a silicate glassovercladded device (+0.01 nm/° C.). A greater impact of the negativedn/dT overclad would have been achieved if the glass overclad had beenmore deeply etched away.

[0076] In another embodiment of the invention, a second bi-layer methodcan be employed. The thin glass overclad method comprises firstdepositing a very thin glass overclad layer on a device followed byovercladding with a negative dn/dT organic-containing material. Across-section of such a waveguide is depicted in FIG. 8. Theoreticaln(T) curves were calculated as described above for the etched glassoverclad method. Curves for a glass overclad thickness of 0.5 μm areshown in FIG. 9. The dn/dT of the organic-containing material becomesmore negative at higher temperatures. The average dn/dT between 0 and70° C. is preferably about (−3.0±0.4)×10⁻⁴° C.⁻¹ for the glass overcladthickness of 0.5 μm. An advantage of the present method is themanufacturability and economical approach of the procedure. In addition,the thickness of the glass overclad can be easily tuned to adjust thechannel wavelength shift to zero. In a preferred embodiment, an optimalglass overclad thickness (tuned thickness) for the device core waveguideand −dn/dT organic containing overclad is determined to minimize channelwavelength shift. The device is then provided with such a tuned glassoverclad thickness which inhibits channel wavelength shift.

[0077] Hybrid Overclad

[0078] In another preferred embodiment of the invention, the hybridoverclad method is employed. In the hybrid method, the overclad ispreferably made by mixing a polymer overclad material with silicanano-particles. The mixture of the negative dn/dT polymer with positivedn/dT silica provides a material with a less negative dn/dT, suitablefor overcladding the device of the invention. The presence of epoxygroups in the polymer and the use of an adhesion promoter such as, forexample, glycidoxypropyl trimethoxysilane or mercaptopropyltrimethoxysilane, or the like, provides compatibility between the glassand polymer and provides good dispersion of the silica particles with nophase separation. Silica nano-particles with diameters smaller than 10nm are preferred and are commercially available. The hybrid materialpolymer/silica nano-particles is transparent in the visible-near IRrange and the domains of different index are preferably too small toincrease the propagation losses at 1.55 μm.

[0079] It will be apparent to those skilled in the art that variousmodifications and variations can be made in the methods, compositions,and devices of the present invention without departing from the spiritor scope of the invention. Thus, it is intended that the presentinvention covers the modifications and variations of this inventionprovided they come within the scope of the appended claims and theirequivalents.

What is claimed is:
 1. An athermalized optical telecommunicationswavelength division multiplexer/demultiplexer integrated waveguidecircuit device, said device comprising: a planar substrate including awaveguide undercladding, which can be a buffer layer or the substrateitself; a doped silica waveguide circuit core supported on said planarsubstrate, wherein said silica waveguide circuit core includes amultiplexing/demultiplexing circuit region formultiplexing/demultiplexing a plurality of optical telecommunicationswavelength channels; an inhomogeneous waveguide circuit overcladdingincluding a first waveguide overcladding material and a second waveguideovercladding material; wherein said device guides opticaltelecommunications light in a waveguide core power distribution, in awaveguide undercladding power distribution and in a waveguideovercladding power distribution, wherein a first portion of light guidedin said waveguide overcladding power distribution is guided through saidfirst waveguide overcladding material and a second portion of lightguided in said waveguide overcladding power distribution is guidedthrough said second waveguide overcladding material such that athermally induced wavelength shift in the channel wavelengths of saidmultiplexing/demultiplexing device is inhibited to less than 0.10 nmwhen said device is subjected to a temperature variation within therange of 0 to 70° C.
 2. The device of claim 1 wherein said thermallyinduced wavelength shift in the channel wavelengths of saidmultiplexing/demultiplexing device is inhibited to less than 0.05 nm. 3.The device of claim 1 wherein said first waveguide overcladding materialis an organic containing optical material and said second waveguideovercladding material is an inorganic optical material.
 4. The device ofclaim 1 wherein said first waveguide overcladding material has anegative variation in refractive index versus temperature and saidsecond waveguide overcladding material has a positive variation inrefractive index versus temperature.
 5. The device of claim 4 whereinsaid first waveguide overcladding material negative variation inrefractive index versus temperature is <−5×10⁻⁵ ° C.⁻¹ and said secondwaveguide overcladding material positive variation in refractive indexversus temperature is >5×10⁻⁶° C.⁻¹.
 6. A method of making anathermalized optical telecommunications wavelength divisionmultiplexer/demultiplexer integrated waveguide circuit devicecomprising: providing a waveguide circuit core supported on a planarsubstrate including a waveguide undercladding, which can be a bufferlayer or the substrate itself; said waveguide circuit core material andsaid waveguide undercladding material having a positive variation inrefractive index versus temperature; said waveguide circuit coreincluding a multiplexing/demultiplexing circuit region formultiplexing/demultiplexing a plurality of optical telecommunicationswavelength channels; providing an inhomogeneous waveguide circuitovercladding including a first waveguide overcladding material and asecond waveguide overcladding material; said first waveguideovercladding material having a negative variation in refractive indexversus temperature and said second waveguide overcladding materialhaving a positive variation in refractive index versus temperature;compensating said positive variation in refractive index versustemperature of said waveguide circuit core, of said waveguideundercladding material and of said second waveguide overcladdingmaterial by said negative variation in refractive index versustemperature of said first waveguide overcladding material, whereineither: light is guided by said waveguide circuit core, said waveguideundercladding material and said first waveguide overcladding material inone part of said device, and guided by said waveguide circuit core, saidwaveguide undercladding material and said second waveguide overcladdingmaterial in the other part of said device; or said first waveguideovercladding material is superimposed on said second waveguideovercladding material such that a first portion of light is guided bysaid waveguide circuit core, said waveguide undercladding material andsaid second waveguide overcladding material, while a second portion oflight is guided by said first waveguide overcladding material; or saidsecond waveguide overcladding material is mixed to said first waveguideovercladding material to produce a hybrid waveguide overcladdingmaterial and light is guided by said waveguide circuit core, saidwaveguide undercladding material and said hybrid waveguide overcladdingmaterial; such that a thermally induced wavelength shift in the channelwavelengths of said multiplexing/demultiplexing device is inhibited toless than 0.10 nm when said device is subjected to a temperaturevariation within the range of 0 to 70° C.
 7. The method of claim 6wherein said thermally induced wavelength shift in the channelwavelengths of said multiplexing/demultiplexing device is inhibited toless than 0.05 nm.
 8. An athermalized optical waveguide device having anorganic-containing overclad comprising fluorinated monomers comprisingpentafluorostyrene, trifluoroethylmethacrylate, glycidyl methacrylate,pentadecafluorooctylacrylate, pentafluorobenzylacrylate,hexafluoropropylacrylate, trifluoroethylacrylate, or a combinationthereof.
 9. The device of claim 8 wherein the organic-containingoverclad comprises trifluoroethylmethacrylate, pentafluorostyrene, andglycidyl methacrylate.
 10. The athermalized optical waveguide device ofclaim 9 wherein said organic-containing overclad comprises about 10-75wt. % pentafluorostyrene, about 25-65 wt. % trifluoroethylmethacrylate,and about 0-30 wt. % glycidyl methacrylate.
 11. The athermalized opticalwaveguide device of claim 9 wherein said organic-containing overcladcomprises about 35-65 wt. % pentafluorostyrene, about 30-50 wt. %trifluoroethylmethacrylate, and about 5-15 wt. % glycidyl methacrylate.12. The athermalized optical waveguide device of claim 8 wherein onepart of said device is overcladded with a silicate glass overclad andthe other part of said device is overcladded with saidorganic-containing overclad.
 13. The athermalized optical waveguidedevice of claim 8 wherein said organic-containing overclad issuperimposed on a silicate glass overclad.
 14. The athermalized opticalwaveguide device of claim 13 wherein said silicate glass overclad isformed by first forming a thick glass overclad and secondly partlyetching the device.
 15. The athermalized optical waveguide device ofclaim 13 wherein said silicate glass overclad is less than 2 μm thick.16. The athermalized optical waveguide device of claim 8 wherein saidorganic-containing overclad is a hybrid overclad also comprising silicaor silicate glass nano-particles.
 17. The device of claim 8 wherein saiddevice comprises a phased array wavelength divisionmultiplexer/demultiplexer.
 18. The device of claim 8 wherein saidorganic-containing overclad comprises pentafluorostyrene,pentadecafluorooctylacrylate, and glycidyl methacrylate.
 19. The deviceof claim 18 wherein said organic-containing overclad comprises about30-80 wt. % pentafluorostyrene, about 20-40 wt. %pentadecafluorooctylacrylate and about 0-30 wt. % glycidyl methacrylate.20. The device of claim 18 wherein said organic-containing overcladcomprises about 55-75 wt. % pentafluorostyrene, about 20-35 wt. %pentadecafluorooctylacrylate, and about 1-10 wt. % glycidylmethacrylate.
 21. The device of claim 8 wherein said organic-containingoverclad comprises pentafluorobenzylacrylate,pentadecafluorooctylacrylate, and glycidyl methacrylate.
 22. The deviceof claim 21 wherein said organic-containing overclad comprises about45-100 wt. % pentafluorobenzylacrylate, about 0-25 wt. %pentadecafluorooctylacrylate and about 0-30 wt. % glycidyl methacrylate.23. The device of claim 21 wherein said organic-containing overcladcomprises about 65-90 wt. % pentafluorobenzylacrylate, about 5-20 wt. %pentadecafluorooctylacrylate, and about 5-15 wt. % glycidylmethacrylate.
 24. The device of claim 18 wherein said organic-containingoverclad is superimposed on a silicate glass overclad.
 25. The device ofclaim from 18 wherein said device comprises a phased array wavelengthdivision multiplexer/demultiplexer.
 26. The device of claim 8 whereinsaid organic-containing overclad further comprises an adhesion promoter.27. An athermalized optical waveguide device that manipulates opticalwavelength channels λ, said device having an integrated opticalwaveguide circuit comprising silica waveguide cores wherein a sol-geloptical material inhibits thermal induced wavelength changes in thechannels.
 28. The device of claim 27 wherein the sol-gel overcladcomprises polydimethylsiloxane, methyltriethoxysilane,phenyltrifluorosilane, and phenyltriethoxysilane.
 29. The device ofclaim 28 wherein the sol-gel overclad comprises molar fractions of about5-15% polydimethylsiloxane, about 60-75% methyltriethoxysilane, about5-15% phenyltrifluorosilane, and about 10-25% phenyltriethoxysilane. 30.The device of claim 29 wherein the sol-gel overclad comprises molarfractions of about 8% polydimethylsiloxane, about 68%methyltriethoxysilane, about 8% phenyltrifluorosilane, and about 16%phenyltriethoxysilane.
 31. The device of claim 27 wherein said devicecomprises a phased array wavelength division multiplexer/demultiplexer.32. The device of claim from 27 wherein one part of said device isovercladded with a silicate glass overclad and the other part of saiddevice is overcladded with said sol-gel overclad.
 33. The device ofclaim 27 wherein said sol-gel overclad is superimposed on a silicateglass overclad.
 34. The device of claim 29 wherein said silicate glassoverclad is formed by first forming a thick glass overclad and secondlypartly etching the device.
 35. The device of claim 33 wherein saidsilicate glass overclad is less than 2 μm thick.
 36. An athermalizedphased array wavelength division multiplexer/demultiplexer integratedoptical waveguide circuit device having a local overclad wherein onepart of said device is overcladded with a silicate glass overclad andthe other part of said device is overcladded with a negative dn/dToverclad material.
 37. The device of claim 36 wherein said negativedn/dT overclad material is a polymer.
 38. The device of claim 37 whereinsaid polymer material comprises pentafluorostyrene,trifluoroethylmethacrylate, and glycidyl methacrylate.
 39. The device ofclaim 37 wherein said polymer material comprises about 10-75 wt. %pentafluorostyrene, about 25-65 wt. % trifluoroethylmethacrylate, andabout 0-30 wt. % glycidyl methacrylate.
 40. The device of claim 37wherein said polymer material comprises about 35-65 wt. %pentafluorostyrene, about 30-50 wt. % trifluoroethylmethacrylate, andabout 5-15 wt. % glycidyl methacrylate.
 41. The device of claim 37wherein said polymer material comprises pentafluorostyrene,pentadecafluorooctylacrylate, and glycidyl methacrylate.
 42. The deviceof claim 37 wherein said polymer material comprises about 30-80 wt. %pentafluorostyrene, about 20-40 wt. % pentadecafluorooctylacrylate andabout 0-30 wt. % glycidyl methacrylate.
 43. The device of claim 37wherein said polymer material comprises about 55-75 wt. %pentafluorostyrene, about 20-35 wt. % pentadecafluorooctylacrylate, andabout 1-10 wt. % glycidyl methacrylate.
 44. The device of claim 37wherein said polymer material comprises pentafluorobenzylacrylate,pentadecafluorooctylacrylate, and glycidyl methacrylate.
 45. The deviceof claim 37 wherein said polymer material comprises about 45-100 wt. %pentafluorobenzylacrylate, about 0-25 wt. % pentadecafluorooctylacrylateand about 0-30 wt. % glycidyl methacrylate.
 46. The device of claim 37wherein said polymer material comprises about 65-90 wt. %pentafluorobenzylacrylate, about 5-20 wt. %pentadecafluorooctylacrylate, and about 5-15 wt. % glycidylmethacrylate.
 47. The device of claim 37 wherein said polymer overcladfurther comprises an adhesion promoter.
 48. The device of claim 36wherein said negative dn/dT overclad material is a sol-gel.
 49. Thedevice of claim 48 wherein the sol-gel overclad comprisespolydimethylsiloxane, methyltriethoxysilane, phenyltrifluorosilane, andphenyltriethoxysilane.
 50. The device of claim 48 wherein the sol-geloverclad comprises molar fractions of about 5-15% polydimethylsiloxane,about 60-75% methyltriethoxysilane, about 5-15% phenyltrifluorosilane,and about 10-25% phenyltriethoxysilane.
 51. The device of claim 48wherein the sol-gel overclad comprises molar fractions of about 8%polydimethylsiloxane, about 68% methyltriethoxysilane, about 8%phenyltrifluorosilane, and about 16% phenyltriethoxysilane.
 52. Anathermalized phased array wavelength division multiplexer/demultiplexerintegrated optical waveguide circuit device having a bi-layer overcladwherein a negative dn/dT overclad is superimposed on a silicate glassoverclad.
 53. The device of claim 52 wherein said device comprises asilica core on a planar substrate, wherein said core contacts a silicaoverclad and wherein said silica overclad contacts said negative dn/dToverclad material.
 54. The device of claim 52 wherein said silicateglass overclad is formed by first forming a thick glass overclad andsecondly partly etching the device.
 55. The device of claim 52 whereinsaid silicate glass overclad is less than 2 μm thick.
 56. The device ofclaim 52 wherein said negative dn/dT overclad material is a polymer. 57.The device of claim 55 wherein said negative dn/dT overclad materialcomprises pentafluorostyrene, trifluoroethylmethacrylate, and glycidylmethacrylate.
 58. The device of claim 55 wherein said negative dn/dToverclad material comprises about 10-75 wt. % pentafluorostyrene, about25-65 wt. % trifluoroethylmethacrylate, and about 0-30 wt. % glycidylmethacrylate.
 59. The device of claim 55 wherein said negative dn/dToverclad material comprises about 35-65 wt. % pentafluorostyrene, about30-50 wt. % trifluoroethylmethacrylate, and about 5-15 wt. % glycidylmethacrylate.
 60. The device of claim 54 wherein said negative dn/dToverclad material comprises pentafluorostyrene,pentadecafluorooctylacrylate, and glycidyl methacrylate.
 61. The deviceof claim 54 wherein said negative dn/dT overclad material comprisesabout 30-80 wt. % pentafluorostyrene, about 20-40 wt. %pentadecafluorooctylacrylate and about 0-30 wt. % glycidyl methacrylate.62. The device of claim 54 wherein said negative dn/dT overclad materialcomprises about 55-75 wt. % pentafluorostyrene, about 20-35 wt. %pentadecafluorooctylacrylate, and about 1-10 wt. % glycidylmethacrylate.
 63. The device of claim 54 wherein said negative dn/dToverclad material comprises pentafluorobenzylacrylate,pentadecafluorooctylacrylate, and glycidyl methacrylate.
 64. The deviceof claim 54 wherein said negative dn/dT overclad material comprisesabout 45-100 wt. % pentafluorobenzylacrylate, about 0-25 wt. %pentadecafluorooctylacrylate and about 0-30 wt. % glycidyl methacrylate.65. The device of claim 54 wherein said negative dn/dT overclad materialcomprises about 65-90 wt. % pentafluorobenzylacrylate, about 5-20 wt. %pentadecafluorooctylacrylate, and about 5-15 wt. % glycidylmethacrylate.
 66. The device of claim 56 wherein said polymer overcladfurther comprises an adhesion promoter.
 67. The device of claim 52wherein said negative dn/dT overclad material is a sol-gel.
 68. Thedevice of claim 67 wherein the sol-gel overclad comprisespolydimethylsiloxane, methyltriethoxysilane, phenyltrifluorosilane, andphenyltriethoxysilane.
 69. The device of claim 67 wherein the sol-geloverclad comprises molar fractions of about 5-15% polydimethylsiloxane,about 60-75% methyltriethoxysilane, about 5-15% phenyltrifluorosilane,and about 10-25% phenyltriethoxysilane.
 70. The device of claim 67wherein the sol-gel overclad comprises molar fractions of about 8%polydimethylsiloxane, about 68% methyltriethoxysilane, about 8%phenyltrifluorosilane, and about 16% phenyltriethoxysilane.
 71. Anathermalized phased array wavelength division multiplexer/demultiplexerintegrated optical waveguide circuit device having a hybrid overcladwherein silica or silicate glass nano-particles are embedded in apolymer matrix.
 72. The device of claim 71 wherein said polymer matrixcomprises pentafluorostyrene, trifluoroethylmethacrylate, and glycidylmethacrylate.
 73. The device of claim 71 wherein said polymer matrixcomprises about 10-75 wt. % pentafluorostyrene, about 25-65 wt. %trifluoroethylmethacrylate, and about 0-30 wt. % glycidyl methacrylate.74. The device of claim 71 wherein said polymer matrix comprises about35-65 wt. % pentafluorostyrene, about 30-50 wt. %trifluoroethylmethacrylate, and about 5-15 wt. % glycidyl methacrylate.75. The device of claim 71 wherein said polymer matrix further comprisesan adhesion promoter.
 76. A method of making an athermalized opticalwaveguide device comprising: providing said device containing awaveguide core; contacting a first portion of said device with a glassoverclad; and contacting a second portion of said device with a polymeror sol-gel overclad.
 77. A method of making an athermalized opticalwaveguide device comprising: providing said device containing awaveguide core; contacting said device with a glass overclad; andcontacting said glass overclad with a polymer or sol-gel overclad. 78.The method of claim 77 wherein after contacting said device with a glassoverclad, the device is etched to expose the top side of said waveguidecore.
 79. The method of claim 77 wherein said glass overclad is lessthan 2 μm thick.
 80. The device of any one of claims 1, 6, 8 or 20wherein said device comprises at least one athermalizing claddingstructure chosen from the group including a bilayer overclad, a localoverclad, and a hybrid overclad.